(1) Field of the Invention
The present invention relates to ultrasound diagnostic devices, ultrasound image analysis methods, and programs thereof that are used to perform ultrasound diagnosis by bringing an ultrasound probe that performs transmission and reception of ultrasound waves into contact with a body surface, and in particular limb joints, of a subject.
(2) Description of the Related Art
In recent years the use of ultrasound diagnostic devices to evaluate disease activity of arthritis, including rheumatoid arthritis, is becoming common. In the evaluation of disease activity, B-mode images and power Doppler images are mainly used. Synovial thickening, synovial fluid retention, and bone erosion may be observed in B-mode images, and synovitis may be observed in power Doppler images.
In addition, methods have been proposed of using ultrasound images to grade disease activity of such conditions. In a case in which power Doppler images are used to grade synovitis levels, grades are determined depending on what proportion of a synovial membrane region that is thickened is occupied by a blood-flow signal that is observed.
In order to objectively quantify disease activity from ultrasound images, eliminating user activity, including subjectivity of the examiner, and quantifying according to certain criteria, is preferable. For example, Takao Koike, New treatment of rheumatoid arthritis using ultrasound investigation, Medical Review Co., Ltd., Mar. 10, 2010, pp. 40-43, proposes having an examiner trace freehand on an ultrasound image an articular cavity lined by a synovial membrane that is thickened, and calculating an occupation ratio of a blood-flow signal in the region traced as a quantitative evaluation value. However, by making the examiner trace the articular cavity in freehand, variations occur in the trace result because a trace of an articular cavity from the same ultrasound image may vary depending on the examiner, and even the same examiner may produce a different trace at different times. As a result, quantification of the occupation ratio of a blood-flow signal varies depending on subjectivity of the examiner.
In order to solve the above technical problem, in Japanese Patent Application Publication No. 2013-056156, for example, a method is proposed of objectively quantifying disease activity by analysis of an articular cavity region by clipping out an articular cavity region after specifying a bone surface. According to this method, subjectivity of the examiner is eliminated, and not only a blood-flow signal, but also image findings such as destruction of bone cortex, narrowing of a joint due to cartilage damage, extension of an articular capsule due to synovial thickening, etc., can be quantitatively evaluated.